Method, system, and system components for wireless tire pressure monitoring

ABSTRACT

Disclosed is a method for monitoring and wirelessly signaling data that contains information on the pressure states prevailing in tires of wheels of a vehicle. In the method, electronic modules that are arranged in the wheels wirelessly transmit the data to control device which is arranged in the vehicle. No data is transmitted during a first mode associated with a standstill state of the vehicle, while the respective electronic module transmits the data to the control device in the form of telegrams, during at least one other mode associated with another state of the vehicle. The respective electronic module at least temporarily transmits n telegrams containing the data per time unit to the control device, n being a function of time.

The invention relates to a method for monitoring and wirelesslysignaling data containing information about the pressure conditionspresent in the pneumatic tires of wheels of a vehicle.

The invention further relates to a system suited therefor, to systemcomponents, such as a controller which is disposed in the vehicle, andan electronic module which is disposed in one of the wheels andwirelessly transmits data to the controller.

The article “Tyre Safety Systems—TSS” from February 2005, published in“automobiltechnische Zeitschrift (ATZ)” (edition 2/2005, VIEWEGpublishing house, Germany), describes tire pressure control systems,wherein a variety of data containing information about the conditionspresent in pneumatic tires of wheels of a vehicle is monitored andwirelessly signaled. As is described in the article based onillustrations 3 and 4, such a known system comprises a plurality ofelectronic modules, which are disposed in the wheels of the vehicle andare also referred to as wheel electronics. By way of sensors, theycapture the conditions present in the respective pneumatic tire, such asthe pressure and temperature, and transmit corresponding data to acentral unit, that is, a central controller disposed in the vehicle (seeillustration 1 in the article). This controller in turn evaluates thedata, for example in order to actuate a tire pressure indicator (seeillustration 5) attached in the interior of the vehicle. Because thewheel electronics units are supplied by a miniature battery, typically alithium battery, care must be taken that little current or energy isconsumed, in order to achieve as long a service life of the battery aspossible. For this purpose, for example, the measurement cycles of thesensors are influenced depending on the vehicle movement (see articlepage 3, paragraph 2.2). The data is therefore captured at shortermeasurement intervals and transmitted only when the vehicle is moving.The data is preferably transmitted in the form of a datagram (seearticle, table 2).

In certain system, controlling the emission of the datagrams can also bedone by an interrogator or carrier transmitter. In this case, a triggersignal is transmitted by the controller in order to activate therespective wheel electronics unit as needed, so that the wheelelectronics unit then captures the data and transmits it to thecontroller. For this solution, a reverse channel and a triggertransmitter and receiver are required. While it is possible in this wayto specifically address the individual wheel electronics units in thewheels in order to detect the exact position allocation of the wheels,for example, this solution requires a certain level of complexity. As isalso described in the article based on illustration 1, rightillustration, newer systems are supposed to eliminate a reverse channeland a trigger transmitter and receiver to the extent possible.

It is also known from EP 1467877 B1 to activate the respective wheelelectronics unit only as needed by way of an interrogator, that is atrigger transmitter, in order to increase the service life the battery.In this document, particularly reliable tire pressure monitoring isachieved in that the system is designed such that the wheel electronicsunit automatically transmits the data at a predeterminable minimumtransmission rate, even if the interrogation signal fails, for whateverreason. In this way, an interrogator may be foregone in the method andsystem described there. However, the data would then only be transmittedat a relatively low transmission rate.

From EP 0915764 B1 a method is known for processing signals of a tirepressure monitoring system, wherein the wheel electronics unitsautomatically transmit data to the controller in the form of datagramsand no specific triggering or interrogation is required. Yet, in orderto also be able to determine the wheel positions without triggeringand/or a reverse channel, it is proposed to provide a plurality ofreceiving antenna on the controller, which jointly process the signalsreceived via the antennas and analyze them for the signal intensitythereof. By cyclically deactivating the individual receiving antennas,it can then be determined what deactivation point results in thegreatest intensity loss in the radio signal, wherein it is assumed thatit must be the antenna located closest to the wheel electronics unit.

This solution thus can completely forego a trigger system, howevergreater complexity is required on the part of the receiving antennas.Furthermore, a method is known which utilizes a duty cycle of 50% LF instandstill and 100% in driving operation, resulting the correspondingenergy consumption.

SUMMARY OF THE INVENTION

It is therefore the object of the present invention to propose a methodand a system or apparatus of the type mentioned above, which overcomethe disadvantages described and still can be implemented with lowcomplexity. In particular a method for monitoring and wirelesslysignaling data and a system suited therefor, as well as the associatedsystem components are to be proposed, by which a reduction in the powerrequirement of the wheel electronics units can be achieved.

The object is achieved by a method having the characteristics of claim 1and by a system, a controller, and an electronic module having thecharacteristics of the relevant independent claim.

It is therefore proposed that during a first mode, which is associatedwith a stopped state of the vehicle, no data is transmitted, and thatduring at least one further mode, which is associated with a differentstate of the vehicle, the data is transmitted in the form of datagramsby the respective electronic module or the wheel electronics unit to thecontroller, wherein at least intermittently the electronic moduleconsecutively transmits a plurality of datagrams containing the samedata in a cumulative manner to the controller.

As a result of this type of transmission, a bundled accumulation of aplurality of datagrams (here also referred to as burst mode) takesplace, so that the required data is transmitted only intermittently tothe controller, but then in a lumped form. This enables the wheelposition to be learned. In this way, the overall transmission durationis shortened, however the actual usage period for transmitting the datais not or only insignificantly shortened due to the accumulation of thedatagrams, so that no data loss occurs.

Advantageous embodiments of the invention will be apparent from thedependent claims.

It is therefore advantageous for the data to be transmitted in the formof a first datagram during a second mode, which is associated with adriving state of the vehicle, and for the data to be transmitted onlypartially in the form of a second datagram, which is shorter than thefirst datagram, during a third mode, which is associated with a startingstate of the vehicle. In this way, another differentiation is madebetween the actual driving state of the vehicle and a starting state,wherein during the starting phase a shorter form of datagrams and/or thelowest possible data volume are transmitted, because particularly inthis state the demand for data is greater. In order to meet thisincreased demand for data on the part of the controller, without placingundue burden on the batteries of the wheel electronics units, thedatagrams are shortened to the necessary minimum. The accumulation ofthe datagrams in turn ensures that the controller safely receives alldata of the plurality of wheel electronics units, which is used, forexample, to differentiate between the axles. This transmission is alsoreferred to here as burst mode, wherein it should clarified that thistransmission is not to be confused with burst radio transmission knownfrom the field of mobile communications.

In this context it is particularly advantageous for the respectiveelectronic module or the wheel electronics unit to consecutivelytransmit a plurality of the second datagrams containing the same data ina cumulative manner to the controller at least or exclusively during thethird mode, which is associated with the starting mode of the vehicle.Thus, if a bundle of a plurality of shortened datagrams is transmitted,preferably in the starting state, it can be ensured within therelatively short starting phase that all required data is transmittedbecause of the higher usage data density. In addition, a reduction inthe power requirement and consequently less impact on the battery of thewheel electronics unit are achieved because of the shortness of thedatagrams, while allocating the positions of the plurality of wheelelectronics units at the same time.

It is also advantageous for the data in the second datagram to containat least or exclusively information about the direction of rotation ofthe respective wheel, and for the direction of rotation to be evaluated,so as to determine whether the respective wheel is located on the leftside or on the right side of the vehicle. As a result of these measures,detecting the approximate wheel position is very easy to do, so that itcan at least be determined from which vehicle side the data istransmitted. For this, no reverse channel and/or trigger transmitterwhatsoever are required. Only the direction of rotation must bedetected. For this purpose, preferably a movement and/or accelerationsensor is used, which is accommodated in the electric module.

It is also particularly advantageous for the data in the seconddatagram, this being the shortened datagram, to contain at least noinformation about the condition present in the respective wheel and/orabout the temperature and/or pressure present in the respective wheel.In this way, the second datagram can also be shortened in the startingmode in that only data which is required for determining the approximateor more precise wheel position is transmitted.

In contrast, it is advantageous for the data in the first datagram tocontain at least information about the pressure condition in the wheeland/or the temperature present there. In this way, the longer datagramis used as extensively as possible in the driving mode. In this contextit is advantageous for the information about the pressure condition tobe determined by way of a pressure sensor that is integrated in thewheel electronics unit or for the information about the temperature tobe determined by way of an integrated temperature sensor.

The controller can preferably also evaluate the data received from therespective module (wheel electronics unit) and/or supplement it withadditional data.

It is also particularly advantageous for the controller and/or awireless receiving means connected thereto, such as an antenna, to bedisposed at varying distances with respect to the wheel axles of thevehicle, and for radio signals received from the respective module to becompared to each other in the controller based on the received fieldstrengths thereof, so as to determine whether the respective wheel islocated on one of the front or on one of the rear wheel axles. In thisway, it is determined in a simple manner on the basis of the receivedfield strengths as to whether the respective wheel electronics unit isattached to a front or rear axle. In this context it is furtheradvantageous for the information about the direction of rotation of therespective wheel contained in the received data to be evaluated based onthe reception-amplifying received signals, so as to determine at whichlocation the respective wheel is. In this way, on the basis of thedirection of rotation, it can therefore first be determined whether therespective wheel is located on the left or right vehicle side, and thenit can immediately be evaluated, on the basis of the received fieldstrengths, whether the wheel is located on a front or rear axle. Insummary, in this way the individual wheel position can be specifically,quickly and easily determined.

BRIEF DESCRIPTION OF THE DRAWINGS

It is also preferable for the controller to provide the data itevaluated and/or supplemented as results data by way of an interface,notably a data bus, to other devices and/or modules installed in thevehicle. The controller can be designed as a central data capturing andevaluation unit, which provides the results data to other devices and/ormodules, such as display apparatuses, by way of a preferablystandardized interface. In this context, it is advantageous for thecontroller to provide the results data in the form of a third datagramby way of the data interface and/or the data bus. This datagram can beconfigured independently of the radio datagrams mentioned above and, forexample, be a standardized data bus datagram, such as for a CAN bus orthe like. It is further advantageous if the duty cycle is switched as afunction of the number of driving cycles—the switch between stopped modeand driving operation—of, for example, 50 from 50%/100% to 0%/100%,which results in further energy savings.

It is further advantageous to activate a stopped mode having a dutycycle of 0% LF after production of the wheel electronics.

The invention will be described hereinafter in more detail based ondifferent embodiments and with reference to the enclosed drawings,wherein:

FIG. 1 shows the different operating modes that are defined for themethod and the system in the form of a state chart;

FIG. 2 shows the method according to the invention, including theindividual steps thereof, in the form of a flow chart;

FIG. 3 is a schematic illustration of the arrangement of the differentsystem components in a vehicle;

FIG. 4 shows a schematic illustration of the design of an electronicmodule according to the invention or the wheel electronics unit; and

FIG. 5 shows the different datagrams employed in the method and thesystem.

FIG. 6 the dependency of the transmission frequency on the driving time.

DETAILED DESCRIPTION

Before FIGS. 1 and 2 and the method according to the invention will beaddressed in more detail, first the basic design of the system accordingto the invention will be explained based on FIGS. 3 and 4.

FIG. 3 shows the basic design and/or the installation of a system in avehicle FZ, wherein electronic modules or wheel electronics units RE areinserted in the individual wheels R1 to R4 of the vehicle, whichwirelessly transmit the data thereof D1* to D4* to a controller STG,which is disposed in the vehicle as a central control unit.

The controller STG is connected to a wireless receiving means in theform of an antenna A in order to receive the radio signals of theindividual wheel electronics units RE and evaluate the data containedtherein. The controller STG is connected to further devices and/ormodules (not shown) by way of a data interface or a data bus andsupplies these with results data D′ obtained from the evaluation of thereceived data D1* to D4* and optionally further additional data.

The controller STG or the antenna is not located at the center of thevehicle FZ, but is preferably disposed asymmetrically to the transverseaxis of the vehicle, which is to say either in the front or in the rearpart of the vehicle. In this way, the radio signals of the individualwheel electronics units RE are received by the antenna A of thecontroller STG with varying received field intensities, whereby it canbe determined whether the respective wheel electronics unit is locatedin the front part V or the rear part H of the vehicle FZ.

FIG. 4 shows the design of a wheel electronics unit RE integrated in awheel in the form of a block diagram. The wheel electronics unitsubstantially comprises a microcontroller CRT, which has an integratedtimer TM and is connected to different sensors S1 to S3. The sensors,for example, are a pressure sensor S1, a temperature sensor S2, and atleast one acceleration sensor S3. The microcontroller CRT processes thedata supplied by the sensors and forwards the data to a transmissionunit TX, which in turn transmits the data D or D* by radio to thecontroller STG.

The mode of operation of the system that is described and of thecomponents thereof, as well as the principle of the method according tothe invention, will now be described in more detail based on FIGS. 1 and2 and FIG. 5:

In the method according to the invention, at least during the startingphase of the vehicle, data D* is transmitted from the respectiveelectronic module or the respective wheel electronics unit RE to thecontroller STG at least intermittently in the form of a plurality ofdatagrams DT*, which contain the same data D* and are consecutivelytransmitted in a cumulative manner.

This mode is denoted as mode BM in FIG. 1 and is therefore also referredto as the accumulation mode or burst mode. This mode is preferably onlyoperated in the starting phase, which is to say in the state in whichthe vehicle transitions from a stopped mode SM into a driving mode FM.The burst mode BM notably refers to the starting phase of the vehicle,during which the individual wheel electronics units RE transmit the dataD* in cumulative, preferably shortened, datagrams DT* to the controllerSTG, which is then able to determine in particular the respective wheelposition based on the data.

Once the starting phase of the vehicle has ended and the vehicle is inthe actual driving mode FM, data D is transmitted in the form of longerdatagrams DT, wherein an accumulation, as in the burst mode, can beforegone. The data transmitted in the driving mode FM should contain allthe information that the wheel electronics unit RE can possibly provideto the controller STG. In contrast, in the burst mode BM only data D*that is required for detecting the individual wheel positions istransmitted, such as information about the direction of rotation RL ofthe wheel and/or an identifier ID or the identity of the wheel itself.

Once the driving state of the vehicle has ended, the second mode FM isexited and a transition into the stopped mode SM takes place. In thismode SM, preferably no data is emitted by the wheel electronics unit RE.As soon as the vehicle FZ starts to move again, which can be detected byway of an acceleration sensor (see S3 in FIG. 4), for example, thetransition into the starting mode or burst mode BM takes place. As isshown in FIG. 1, the state of the vehicle from a first mode SM, whichdescribes the stopped state of the vehicle, into a second mode FM, whichdescribes the driving state of the vehicle, is switched by way of anintermediate mode, which corresponds to a further mode, this being theburst mode BM. This third mode BM relates to the respective startingstate of the vehicle.

Based on FIG. 2, the method 100, including the steps 110 to 130 thereof,will now be described in more detail, with reference also being made toFIGS. 1 and 5.

The method 100 begins with a step 110, in which a switch is made fromthe first mode SM into the third mode BM, the starting mode. This isdetected, for example, based on acceleration sensors (see sensor S3 inFIG. 4) and can also be controlled based on a timer (see timer TM inFIG. 4) such that this mode BM is maintained only for a limitedduration. In a step 115, the data transmission is carried out for thismode BM in that the respective module or the wheel electronics unit REtransmits the data D* in a plurality of accumulated datagrams to thecontroller STG.

As is shown in FIG. 5, the particular wheel electronics unit REtransmits a shortened datagram DT*, which comprises only some data D* ofthe customarily plurality of data D, which in the normal driving mode FMis transmitted in longer datagrams DT. The short datagram DT*, forexample, is a 9-byte datagram, which contains at least one uniqueidentifier ID for the respective wheel electronics unit RE, and thusalso for the respective wheel, and information RL indicating thedirection of rotation of the respective wheel. Even based on theidentifiers ID, the controller STG can check whether all wheelelectronics units RE are operational or whether at least four differentidentifiers ID and thus wheels are being detected. In addition, based onthe information RL, the controller STG can detect whether the respectivewheel is located on the left or right side of the vehicle. For example,if based on the information RL it is indicated that the wheel is turningclockwise, it is assumed that the wheel is located on the right vehicleside R. In the other case, it is assumed that the wheel is located onthe left vehicle side L. In this way, based on such little information,an initial localization of wheels can be carried out.

In step 115, additionally the received field strengths of therespectively received signals are evaluated by the controller STG andcompared to each other. Because the controller or the antenna A (seealso FIG. 3) is located closer to the front of the vehicle or the tailof the vehicle, based on the received field strengths it is easy todetermine whether the respective wheel electronics unit RE is located ona front axle V or on a rear axle H of the vehicle FZ. In conjunctionwith the previously determined side and/or the direction of rotation ofthe wheel electronics unit (left or right vehicle side), in this way, aprecise position determination of the individual wheels is achieved.Thus, if based on the information RL, for example, a wheel turningclockwise is indicated, and if a relatively high received field strengthis detected by the controller STG in the case that the antenna A ismounted closer to the front axles, it can be assumed that this wheel islocated on the right vehicle side R on the front axle V. With respect tothe illustration of FIG. 3, in this way the position of the wheel R2would be clearly detected. The detection of the remaining wheels iscarried out in an analogous procedure. In step 115, clear and uniquepositioning of the individual wheels is possible already based on theshort datagrams DT*, and in step 115 a current pressure indication inthe FZ is also possible based on individual DT.

In addition, transmitting shortened datagrams DT* in an accumulatedmanner, or in the burst mode, ensures that the required data is receivedcompletely and correctly by the controller STG. In addition to theinformation ID and RL already mentioned above, the shortened datagramDT* can also contain further data, such as synchronization data and testdata, such as checksum data.

In total, however, the datagram DT* is clearly shorter than theconventional datagram DT. For example, the datagram DT* comprises only 9bytes, while the longer datagram DT comprises 15 bytes. As is shown inFIG. 5, the longer datagram DT, which is transmitted in the laterdriving mode FM, may also contain information about the pressure stateDRK and about the temperature T in the respective tire. This data iscaptured by way of the appropriate sensors, these being the pressuresensor S1 and the temperature sensor S2 (see FIG. 4). In addition, thedatagram DT may also contain information RZ about the residual servicelife of the battery.

The method proposed here utilizes the above-mentioned burst mode BMrepresenting an accumulation of shortened datagrams DT* fortransmissions while starting to move the vehicle. Within a short timeperiod, such as 1 minute, in this way many datagrams DT* having the sameor at least a similar data content are transmitted. Because of this typeof transmission, very fast wheel allocation is possible, whereinadditionally energy is saved because of the shortened datagram length,for example, from 15 bytes to 9 bytes. If, for example, 25 datagrams areconsecutively transmitted in an accumulation, a reduction of the powerdemand by approximately 40% is achieved given the shortening of thedatagram DT* compared to the regular datagram DT. This is achievedwithout any loss of information whatsoever.

Once the starting phase or the mode BM has ended, in a step 120 a switchis carried out to the next mode, this being the mode FM, which relatesto the driving state of the vehicle. In a step 125 then, the longerdatagram DT is used in order to transmit all captured data D to theextent possible from the respective wheel electronics unit RE to thecontroller STG. In this mode FM as well, an accumulated transmission ofthe datagram DT may, but does not have to, take place. In a step 130,after ending the path state, a transition takes place into the stoppedstate, this being the mode SM. As was already described above, no datatransmission is carried out in this first mode SM.

The different modes overall thereby enable optimal data transmissionwith respect to the information content and energy savings. Because ofthe proposed differentiation between the actual driving state and thestarting state of the vehicle, optimized data transmission by way ofshortened datagrams is enabled, notably for the starting phase of thevehicle.

In addition to the actual data transmission between the respective wheelelectronics unit RE and the controller STG, the invention also comprisesa further transmission of result data DT′ (see FIG. 5) from thecontroller STG to further devices or modules installed in the vehicle,such as display apparatuses in the instrument panel.

For this purpose, the controller STG evaluates the received data D or D*and supplements it optionally with further data D+, so as to formresults data D′. This data is transmitted, for example, by way of astandardized bus data datagram DT′ to the further devices or modules. Astatus bit or byte ST, for example, which relates to the received fieldstrengths determined by the controller STG and which indicates whetherthe respective wheel electronics unit RE is located on a front axle orrear axle of the vehicle, can be regarded as additional data D+. Thestatus bit ST can thus take on the state V or the state H (see FIG. 3).In conjunction with the information RL which can take on the status L orR and is transmitted by the wheel electronics unit, it provides a uniquewheel allocation.

The method described here, and the apparatuses and units carrying outthe method relate to particularly advantageous embodiments and shouldnot be interpreted as restrictive. The scope of protection of theinvention rather also comprises further modifications and is determinedin particular by the wording of the claims.

LIST OF REFERENCE NUMERALS

-   -   SM First mode (stopped mode)    -   FM Second mode (driving mode)    -   BM Third mode (burst mode)    -   100 Method comprising (partial) steps 110-130    -   DRK Information about pressure conditions in wheels (R1-R4)    -   FZ Vehicle    -   STG Controller    -   A Antenna    -   BUS Interface or data bus    -   R1-R4 Wheels    -   RE Electronic module or wheel electronics unit    -   S1, S2, S3 Different sensors for pressure (S1), temperature (S2)        and acceleration (S3)    -   CRT Microcontroller    -   TX Transmitter (in wheel electronics unit)    -   D Data (regular scope) of wheel electronics unit    -   D* Data (shortened scope) of wheel electronics unit    -   D+Additional data from controller    -   D′ Results data from controller (for data bus)    -   DT Datagram (regular)    -   DT* Datagram (shortened)    -   DT′ Datagram (for results data on data bus)    -   ID, RL, DRK,    -   T, RZ, ST Data or information about respective wheel/tire,        particularly identifier (ID), right-left (RL), pressure (DRK)    -   SYNC,    -   CRC1, CRC2 Data regarding synchronization or for plausibility        check (checksum)

The invention claimed is:
 1. A method for monitoring and wirelesslysignaling data containing information about a pressure condition presentin pneumatic tires of wheels of a vehicle, the data being transmittedwirelessly by electronic modules disposed in the wheels to a controllerdisposed in the vehicle, wherein a first mode is associated with astopped state of the vehicle, wherein the data is transmitted in a formof datagrams by a respective electronic module to the controller duringa second mode associated with a starting state of the vehicle, whereinthe data is transmitted in the form of datagrams by the respectiveelectronic module to the controller during a third mode associated witha driving state of the vehicle, wherein the datagrams containing thedata are transmitted per n unit of time to the controller by therespective electronic module intermittently with n being a function oftime, wherein the third mode of the driving state comprises a lowertransmission rate as compared to the second mode of the starting state.2. The method according to claim 1, wherein the data is transmittedduring a fourth mode with an even lower transmission rate as compared tothe third mode, the fourth mode being associated with a second drivingstate of the vehicle.
 3. The method according to claim 2, wherein thefourth mode begins approximately 15 minutes after starting to drive. 4.A method for monitoring and wirelessly signaling data that containsinformation on a pressure in tires of wheels of a vehicle, wherein thedata are transmitted wirelessly in a form of telegrams by electronicmodules disposed in the wheels to a control device disposed in thevehicle, the electronic modules being switched by an acceleration sensorfrom a first mode which is assigned to a standstill state of the vehicleto a starting mode which is assigned to a starting-off state of thevehicle, the electronic modules send in the starting mode telegramswhich contain information on a direction of rotation or anidentification and which are shortened by containing no information on atemperature in the wheel.
 5. A method for monitoring and wirelesslysignaling data that contain information on a pressure in tires of wheelsof a vehicle, wherein the data are transmitted wirelessly in a form oftelegrams by electronic modules disposed in the wheels to a controldevice disposed in the vehicle, the electronic modules being switched byan acceleration sensor from a first mode which is assigned to astandstill state of the vehicle to a starting mode which is assigned toa starting-off state of the vehicle, the electronic modules send in thestarting mode telegrams which contain information on a direction ofrotation or an identification and which are shortened by containing noinformation on the pressure in the wheel.